Solute-mediated interactions between active droplets

Journal article (2017)

Authors

Pepijn G. Moerman Universiteit Utrecht, New York University
Henrique W. Moyses New York University
E.B. van der Wee Universiteit Utrecht
David G. Grier New York University
Alfons van Blaaderen Universiteit Utrecht
Willem K. Kegel Universiteit Utrecht
Jan Groenewold South China Normal University, Universiteit Utrecht
Jasna Brujic New York University
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Published Date

2017

Language

English

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Abstract

Concentration gradients play a critical role in embryogenesis, bacterial locomotion, as well as the motility of active particles. Particles develop concentration profiles around them by dissolution, adsorption, or the reactivity of surface species. These gradients change the surface energy of the particles, driving both their self-propulsion and governing their interactions. Here, we uncover a regime in which solute gradients mediate interactions between slowly dissolving droplets without causing autophoresis. This decoupling allows us to directly measure the steady-state, repulsive force, which scales with interparticle distance as F∼1/r2. Our results show that the dissolution process is diffusion rather than reaction rate limited, and the theoretical model captures the dependence of the interactions on droplet size and solute concentration, using a single fit parameter, l=16±3nm, which corresponds to the length scale of a swollen micelle. Our results shed light on the out-of-equilibrium behavior of particles with surface reactivity.